What is a key feature of conjunctivitis caused by allergies?

• A. Redness without itching.
• B. Purulent discharge and crusting.
• C. Itching and red eyes.
• D. Painful eye with vision loss.

Answer: (C)

Itching with red eyes is the hallmark of allergic conjunctivitis. Exposure to an allergen triggers mast cells in the conjunctiva to release histamine and other mediators, causing intense itching along with conjunctival redness and tearing. The itch is the distinguishing feature that helps separate it from other causes of conjunctivitis. Purulent crusting and discharge point more toward bacterial conjunctivitis, which has thick, purulent discharge rather than itch. A painful eye with vision changes suggests something more serious like keratitis or uveitis, not typical allergic inflammation. Redness without itching can occur with non-allergic irritants or infections, but the presence of itching makes allergic conjunctivitis the best fit.